This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-342814 filed on Nov. 10, 2000.
The present invention relates to automatic headlight axis direction control system and method that adjust automatically the axis of light emitted by a headlight of a vehicle.
Conventionally, an automatic headlight axis direction control system that uses a DC motor as an actuator to adjust a headlight axis direction of a vehicle is proposed. A certain position equivalent to an actual headlight axis direction is detected by a potentiometer or the like as a position detection sensor disposed side-by-side to the DC motor after a DC current is applied to the DC motor. Subsequently, the headlight axis is moved by the DC motor to a direction predetermined on a basis of the position detected by the potentiometer. Therefore, a headlight axis direction control using the DC motor provides an advantage that the headlight axis direction control is able to be started immediately when a headlight switch is turned on because the headlight axis direction is monitored in real time.
However, the DC motor is not driven until the headlight axis direction control is needed. Thus, whether a failure exists in a driving system for the DC motor is not detected before the axis control is started.
Therefore, only after the headlight switch is turned on, the failure is detected for the first time if a driver is enabled to recognize a deviation from the normal headlight control characteristic. Unless the driver perceives the failure, the vehicle travels with the failure in the headlight and the headlight axis direction control is not performed at all.
Furthermore, if there is a significant deviation from the normal headlight control characteristic due to a failure in the DC motor driving system, as a result, oncoming traffic incurs glaring light and/or adequate forward visibility is not provided.
It is an object of the present invention to provide automatic headlight axis direction control system and method that include a function that a failure in a driving system of an actuator used for adjusting a headlight axis direction of a vehicle is detected before a light axis direction control is started, thereby improving reliability the headlight axis direction control.
According to the present invention, an actuator is driven with a predetermined current output thereto before a headlight axis direction control is started by using a headlight axis control angle calculated on a basis of a variety of sensor information. At that time, if there is no variation in an output from a potentiometer, a failure in the driving system of the actuator is decided to exist. Therefore, for example, if failure detection is implemented when an ignition switch to start an engine is turned on, the failure in the driving system of the actuator is detected before the headlight needs to be turned on.